In a semiconductor manufacturing process, a micro patterning process has conventionally been performed on a surface of an object to be processed such as a semiconductor wafer by means of, e.g., a plasma etching apparatus.
In such a plasma etching apparatus, an upper and a lower electrode are installed to face each other in an airtight chamber of a plasma processing vessel thereof. Mounted on the lower electrode is the object to be processed. When high frequency electric powers are applied to the upper electrode and the lower electrode, a glow discharge is induced therebetween. A process gas supplied into the chamber of the plasma processing vessel is converted into plasma by the glow discharge, which enables the object to be patterned by the plasma etching. As the process gas, a CF(Fluorocarbon)-based gas has been widely used.
The plasma processing vessel of the plasma etching apparatus is made of alumite treated Al (aluminum) employed as a base material. Further, ceramic members made of sintered Al2O3 (alumina) are detachably mounted on an entire inner surface of the chamber.
That is, the plasma processing vessel used in the prior art plasma etching apparatus includes an outer wall portion made of Al and an inner wall portion made of the ceramic material of Al2O3 (alumina), the inner wall portion being detachably mounted on the inner surface of the outer wall. Therefore, even in a case where the inner wall portion of the plasma processing vessel is abraded and damaged by plasma, restoration can be achieved by simply replacing the inner wall portion with a new one.
Further, in order to perform a desired etching process on the object in the prior art plasma etching apparatus by effectively confining the plasma between the upper electrode and the lower electrode, plasma-resistant members such as a focus ring, a discharge ring and the like (referred to as in-chamber members hereinafter) are disposed at predetermined positions around the upper and the lower electrode.
In case of the above-described conventional plasma etching apparatus employing a CF-based gas as a main process gas, however, reaction by-products (CF-based polymers) of the plasma process are deposited on the inner wall of the chamber. The by-products deposited for a certain period of time are separated and dispersed to become foreign substances. In order to prevent the foreign substances from being generated, the in-chamber members are periodically cleaned by wet cleaning.
FIGS. 3A to 3D show views setting forth a cleaning process of a conventional in-chamber member. Specifically, FIG. 3A depicts a view illustrating a state before CF-based polymer particles are deposited on the in-chamber member; 3B presents a view illustrating a state after the CF-based polymer particles are deposited on the in-chamber member; FIG. 3C represents the in-chamber member after cleaning; and FIG. 3D offers a view illustrating a physical removing process of residual CF-based polymer particles.
When the etching process is performed in the chamber of the plasma etching apparatus, an in-chamber member 60 undergoes a change from the state where the CF-based polymer particles are not deposited thereon as shown in FIG. 3A to the state where the CF-based polymer particles are deposited thereon as shown in FIG. 3B, i.e., a deposition state. When such a state is reached, the periodic cleaning work is performed. The periodic cleaning is carried out by immersing the in-chamber member 60 in a cleaning fluid or a peeling solvent. By only immersing the in-chamber member 60 in the cleaning fluid or the like, however, deposits 61 cannot be completely removed from the in-chamber member 60 and a portion thereof remains as shown in FIG. 3C. For this reason, it is required to physically remove the residues, e.g., by using a scoop as shown in FIG. 3D or by blast.
However, in case where the residues are removed by the above-explained physical method, the number of processes of the periodic cleaning work increases to that extent, which in turn increases the time and the cost required for the cleaning work. Furthermore, there may arise a problem that the in-chamber member 60 is physically damaged. For this reason, it may be considered to use rather stronger cleaning fluid and peeling solvent to avoid employing the physical method for removing the residues. In this case, however, there may arise another problem that the in-chamber member 60 is chemically damaged, e.g., corroded, due to the cleaning fluid and the like capable of completely eliminating the residues.